This invention relates generally to a solenoid, and more particularly concerns extending the life of the solenoid.
As a solenoid assembly wears, the surface between the solenoid plunger and the solenoid housing loses its low friction coating. This loss of low friction coating causes the pull in and drop out times of the solenoid assembly to increase in length eventually translating to a failure in timing or reduced stroke. This loss of low friction coating often occurs on the top and bottom of the plunger surfaces at opposite points as a result of side loads within the solenoid assembly.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,558,293 to Haneda et al. discloses a solenoid assembly comprising a magnetic plunger, an electric coil for generating a magnetic flux in a direction along an axis of the magnetic plunger, a main yoke composed of at least two separate members for defining a magnetic flux passage around the electric coil, and a pair of yoke end members held in engagement respectively with opposite ends of the main yoke, an outer casing. The yoke and members have recesses extending substantially normally to the axis of the magnetic plunger, and the main yoke has projections fitted respectively in the recesses to maintain the main yoke and the yoke end members in engaging relationship. The outer casing has an inner wall keeping the main yoke held in engagement with the yoke end members. A leaf spring acts on the main yoke to hold the latter securely in place in the outer casing. The yoke end members have cylindrical projections supporting thereon the electric coil between the projections of the main yoke. Magnetic cores are firmly held against a permanent magnet by resilient members fitted in slots defined in outer peripheral surface of a plunger shaft.
U.S. Pat. No. 5,417,403 to Shurman et al. discloses a solenoid valve including a valve housing having a central bore and a valve seat, a valve element movable between an open position allowing fluid to pass through said valve seat and a closed position in sealing engagement with said valve seat, a valve operator for moving the valve element between the open and closed positions including a reciprocating armature plunger member extending through the bore and an armature secured to the armature plunger, a valve adjustment for adjustably mounting the valve element relative to the valve operator for permitting adjustment to within an acceptable tolerance of a predetermined distance between the valve element and the valve seat when the valve element is in its open position without creating a path of leakage when the valve element is in its closed position. A valve adjustment securing mechanism is provided for securing the armature to an armature end of the armature plunger and a load bearing insert is secured within the armature for bearing a load exerted by the armature plunger during reciprocation of the valve element to allow for surface contact during the valve operation without surface wear.